Plugin.js

const semver = require('semver')
const version = require('./package.json').version

class Plugin {
  constructor(userPlugin, pluggageVersion) {
    pluggageVersion = pluggageVersion || version

    this._userPlugin = userPlugin

    if (!userPlugin) {
      throw new TypeError('missing plugin implementation')
    }

    if (typeof(userPlugin.init) !== 'function') {
      throw new TypeError('missing init() method in plugin implementation')
    }

    if (typeof(userPlugin.shutdown) !== 'function') {
      throw new TypeError('missing shutdown() method in plugin implementation')
    }

    if (!isValidSemver(pluggageVersion)) {
      throw new TypeError(`version "${pluggageVersion}" is not a valid semver version`)
    }

    this._pluggageVersion = pluggageVersion
  }

  /**
   *	create a plugin interface
   *
   *	@param {object} plugin - an object with an init() and shutdown() methods
   *	@param {string} _versionOverride - a semver version, this is used for testing purposes
   *										mostly.
   *
   */
  static create(userPlugin, overrideVersion) {
    return new Plugin(userPlugin, overrideVersion)
  }

  get version() {
    return this._pluggageVersion
  }

  init(hostApi) {
    return this._userPlugin.init(hostApi)
  }

  shutdown() {
    return this._userPlugin.shutdown()
  }
}

function isValidSemver(version) {
  return semver.valid(version) !== null
}

module.exports = Plugin